JPH021106B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel wood-based composite board. Traditionally, wood-based composite boards include particle board using wood chips and adhesive, fiber board using wood or other plant fibers and adhesive, wood wool cement board using wood wool and cement, and wood cement board using wood chips and cement. The following products are manufactured: cement boards made from wood chips, pulp cement boards made from pulp and cement, and wood fiber cement boards made from wood fibers and cement. Among these wood-based composite boards, particle board and fiber board are pressure-formed using a small amount of organic binder as an adhesive, so they have physical properties such as strength, lightness, and workability that are close to those of wood. However, since it is inferior in flame retardancy, there are problems in terms of fire retardant performance when used as interior and exterior building materials. On the other hand, wood wool cement boards, wood chip cement boards, pulp cement boards, wood fiber cement boards, etc. are molded using a large amount of inorganic Portland cement as an adhesive, so their physical properties such as strength, lightness, and workability are poor. Although it is often inferior to particle board and fiber board, it has excellent performance such as flame retardancy and weather resistance, so it has a wide range of uses as an interior and exterior building material. However, wood wool cement board, wood chip cement board,
Wood-cement composite materials such as pulp cement boards and wood fiber cement boards use Portland cement as a binder, so depending on the tree species, certain water-soluble components in the wood may inhibit hardening of the cement. The basic performance required when using wood cement boards as interior and exterior materials is high strength as a base material, and the bonding strength of this wood cement board is:
Problems can be broadly divided into two types: problems mainly caused by the wood, such as the shape of the wood, surface properties, and chemical components of the wood, and problems mainly caused by the cement, such as the type of cement, additives, curing conditions, etc. can. The main components of wood are cellulose, lignin, and hemicellulose, with 5 to 10 other subordinate components.
Contains %. Conventionally, in the production of wood-cement composite materials, coniferous trees such as larch, red cedar, and russet pine were used, and hardwoods such as maple, white pine, and pine were used.
Haywood, and bark in general, is also known to cause poor cement hardening. Therefore, in severe cases, the hardening of the cement may be significantly inhibited, reducing the number of times the formwork or curing chamber can be used, or the product may fail. The reason why cement hardens poorly depending on the tree species is that among the components extracted by water or alkali in the wood, harmful components such as humic acid, sugar, and lignin, which have a negative effect on cement, are present around the cement particles. It is said that this is because it forms a film on the cement and inhibits the hydration of the cement. For this reason, the types of trees used in the production of wood-cement composite materials are limited, and as a countermeasure, the wood raw materials are soaked in water or alkali, heat treated, treated with paraformaldehyde, or treated with calcium chloride or magnesium chloride. Adding hardening accelerators such as This is a contributing factor to the increase. Furthermore, wood-cement composite boards using Portland cement as a binder have a slow hardening process during manufacture, resulting in the spring-bagging phenomenon of the wood raw material (a phenomenon in which the molded product loosens when it is decompressed after compaction, which adversely affects strength properties and other properties). happens. For this reason,
Traditionally, when manufacturing wood-cement composite boards,
It is said that the board must be cured for two days and nights while being pressurized, but in the wood cement board industry, in order to shorten board manufacturing time, the product is artificially dried immediately after forming and pressing. In many cases, it is inevitable that the cement's strength increase will almost stop from that point on. Furthermore, the wood-cement composite board needs to be dried after pressure curing, and it has been impossible to perform pressure curing and heat drying at the same time. This is because the binder is Portland cement, so if it dries during the curing process, the hydration of the Portland cement will not proceed and the hardening phenomenon will stop. Another disadvantage of wood-cement composite boards is that the binder is Portland cement, so the molded product exhibits alkalinity.Therefore, there is a concern about corrosion of the wood, and it is necessary to treat the wood raw material with chemicals to improve its decay resistance. It's normal. Due to the fact that the molded body is alkaline as described above, when painting the surface of a wood-cement composite board, the paint is required to have alkali resistance, which naturally places restrictions on the paint. As a result of various researches on how to improve the various defects of the conventional wood-based composite boards mentioned above and create a composite material that takes advantage of the characteristics of both wood and inorganic binder, the present inventor has finally found a way to improve the various defects of the conventional wood-based composite boards. We have now invented a method for manufacturing wood composite boards made of a new inorganic binder with a new composition. That is, in the present invention, the combination of coal ash (including fly ash and hearth bottom ash) generated from coal-fired power plants, etc. and an aqueous solution of phosphoric acid or its salt to 5 to 50 parts by weight of the wood cutting material is P ₂ O _{5 .} /0.05 by weight ratio of coal ash
An inorganic binder with a composition of ~0.5 to 95 to 50
This is a method for manufacturing a wood-based composite board characterized by adding parts by weight, mixing, and forming. The inorganic binder according to the present invention is completely different from Portland cement and consists of an aqueous solution of coal ash and phosphoric acid or its salt. As the phosphoric acid, in addition to orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, hypophosphoric acid, phosphorous acid, and hypophosphorous acid are used. Note that, if necessary, 1 to 20% by weight of the coal ash can be replaced with at least one member selected from oxides or hydroxides of magnesium, calcium, aluminum, iron and silicon, and asbestos. By combining with phosphoric acid, these produce an amorphous gel-like hydrous phosphoric acid compound, which exhibits extremely strong adhesive properties and penetrates into wood, providing flame retardancy, which is an important physical property for building materials. will be granted. The present inventors believe that if this new inorganic binder is used in the production of wood composite boards, curing failure due to water-soluble components in the wood will not occur at all, and the curing time will be quick, so the pressure compaction and curing period will be reduced. Furthermore, if necessary, the thermosetting properties of this inorganic binder can be used to perform pressing and heat curing at the same time, allowing hardening and drying to be performed at the same time. The reason for this is not clear, but the hardening mechanism of this inorganic binder is not based on the formation of calcium silicate hydrate under saturated lime liquid conditions, like the hardening mechanism of Portland cement, but rather is based on the formation of calcium silicate hydrate, which is the main component of coal ash. activated Al ₂ O ₃ , SiO ₂ ,
This is thought to be because a plurality of components such as Fe ₂ O ₃ , CaO, and MgO generate adhesive components and lead to hardening in the presence of phosphoric acid-containing liquids such as various phosphoric acids and phosphate aqueous solutions. In the present invention, the reason why the mixing ratio of the wood cutting material and the inorganic binder is limited to 5 to 50 parts by weight of the wood cutting material and 95 to 50 parts by weight of the inorganic binder is that when the wood cutting material is less than 5 parts by weight, the wood This is because the lightness and workability of the composite board are impaired, and if the amount exceeds 50 parts by weight, the strength characteristics and flammability are impaired. The reason why the composition of the inorganic binder was limited to 0.05 to 0.5 in terms of P ₂ O ₅ /coal ash weight ratio is that if it is less than 0.05, the strength of the cured product will decrease significantly due to insufficient P ₂ O ₅ , and if it exceeds 0.5, P This is because excess ₂ O ₅ impairs physical properties such as water resistance. The reason for limiting the amount of inorganic material to replace the coal ash mentioned above to 1 to 20 parts by weight based on the weight of coal ash is that less than 1 part by weight is effective in improving the strength characteristics of the inorganic binder and shortening the hardening speed. This is because the amount of the inorganic binder is small, and even if it is added in an amount exceeding 20 parts by weight, the effect of increasing the strength of the inorganic binder and shortening the curing speed will not be enhanced. In addition, during molding, press pressure should be set at 1 to 100 kg/cm ² ,
The reason why we limited the heating temperature to 20 to 200℃ is that 1Kg/
If it is less than 100 kg/cm ² , the strength of the molded product is extremely low and cannot be put to practical use, and if it exceeds 100 kg/cm ² , the bulk specific gravity will increase, causing problems with lightness and workability. This is because if the temperature is too low, the curing time will not be much different from the curing time at room temperature, and the purpose of shortening the curing period will no longer be achieved, and if it exceeds 200°C, there is a risk that some of the wood cutting material will char. According to the present invention, the pH of the cured product is weakly acidic to neutral, and the phosphorus compound has a wood preservative effect, which improves the decay resistance of wood-based composite boards and eliminates restrictions on paints when painting the surface. It is effective. Furthermore, according to the present invention, by adjusting the concentration of the various phosphoric acids and phosphate aqueous solutions mentioned above or the amount added to coal ash, it is possible to adjust the curing speed and strength characteristics. Depending on the situation, it is possible to shorten the curing time and increase the strength by using various additives in combination or by employing heating operations, which improves the productivity, reduces weight, and reduces the price of wood-based composite boards. etc. can be expected. Next, the present invention will be explained in more detail with reference to Examples. The chemical composition of the coal ash used in the following examples is shown in Table 1.

[Table] Also, the wood materials used in these examples will be explained. In general, in the production of wood wool, wood chip cement boards, etc., Siberian larch (total dry specific gravity
0.57), and Siberian Scots pine (total dry specific gravity 0.40) was used as a tree species that does not cause poor curing. Generally, the causes of poor hardening of cement are:
It is said to be a water-soluble component mainly contained in wood, and the amount of cold water extractable components determined according to JIS P8004-1959 is shown in Table 2.

[Table] In the case of wood chips, the shape of the wood material used was obtained by dividing the wood chips produced using a Perlman flaker and thoroughly air-drying the pieces with a size of 5 to 20 mesh. For hair, the length is 6 cm,
It has a width of 4 mm and a thickness of 0.4 mm and has been thoroughly air-dried. The board was manufactured and tested by mixing wood raw materials and an inorganic binder, forming the mixture into a 15 cm x 20 cm board molding frame, and then pressing it to a predetermined press pressure. After being pressure-tightened for a predetermined period of time, it was depressurized and demolded, and after curing for a predetermined period of time, bulk specific gravity was measured and a bending strength test under central concentrated load was conducted. The bending strength test is based on JIS A1408.
Length according to "Bending test method for architectural boards"
20cm, width 15cm, span 15cm, loading speed 5mm/
It was measured with a centrally concentrated load as min. Example 1 70 parts by weight of coal ash was added to 30 parts by weight of larch wood chips that had not been soaked in water, and after mixing, a crude phosphoric acid solution (concentration of 30.5% in terms of P ₂ O ₅ ) obtained by wet phosphoric acid production was obtained.
Parts by weight were added, kneaded, and formed into a mold. This was pressed at a press pressure of 20 kg/cm ² for 24 hours, then decompressed and air-dried at room temperature for 7 days, and its bulk specific gravity and bending strength were measured. For comparison, 70 parts by weight of ordinary Portland cement was added to 30 parts by weight of larch wood chips, mixed, and 40 parts by weight of water was added.
Tests were also carried out on products that were added in parts by weight, kneaded, formed into a mold, compressed at a press pressure of 10 kg/cm ² for 72 hours, released from the mold, and cured for 14 days. The results were as shown in Table 3.

[Table] Example 2 A comparative test was conducted in exactly the same manner as in Example 1 using larch wood chips that had been soaked in water for 24 hours to remove the water-soluble components in the wood. The results were as shown in Table 4.

[Table] Example 3 67 parts by weight of coal ash and 3 parts by weight of aluminum hydroxide were added to 30 parts by weight of larch wood chips that had not been soaked in water, and after mixing, crude phosphoric acid (30.5% concentration in terms of P ₂ O ₅ ) was added. Parts by weight were added, kneaded, and formed into a mold. This was pressed at a press pressure of 20 kg/cm ² for 6 hours, then decompressed and molded ^, and air-dried at room temperature for 7 days.
The bulk specific gravity and bending strength of the pieces that were pressed for 6 hours at ℃ and subjected to pressure curing and heat drying at the same time were measured. The results were as shown in Table 5.

[Table] Example 4 A comparative test was conducted in exactly the same manner as in Example 1 using pieces of Scots spruce that had not been subjected to water immersion treatment. The results were as shown in Table 6.

[Table] Example 5 67 parts by weight of coal ash and 3 parts by weight of magnesium oxide were added to and mixed with 30 parts by weight of Scots spruce wood chips that had not been soaked in water, and 67 parts by weight of coal ash and 3 parts by weight of asbestos were added to 30 parts by weight of Scots pine wood chips. 40 parts of crude phosphoric acid (30.5 concentration calculated as P ₂ O ₅ )
Parts by weight were added, kneaded, and formed into a mold. After pressing these at a press pressure of 20 kg/cm ² for 12 hours, the molds were released and air-dried for 7 days at room temperature, and their bulk specific gravity and bending strength were measured. The results were as shown in Table 7.

[Table] Example 6 Using larch wood wool and Scots pine wool that have not been soaked in water, 40 parts by weight of the wood wool was mixed with 60 parts by weight of coal ash, and then crude phosphoric acid (concentration of 30.5% in terms of P ₂ O ₅₎ was added. ) 40
Parts by weight were added, kneaded, and formed into a mold. This was pressed at a press pressure of 6 kg/cm ² for 24 hours, then depressurized and demolded, and air-dried and cured at room temperature for 7 days.
For comparison, these wood wools were mixed by adding 60 parts by weight of ordinary Portland cement to 40 parts by weight of the wood wool, then adding 60 parts by weight of water, kneading, forming into a formwork, and pressing at a pressure of 2 kg. /cm ² for 72 hours, the mold was released and cured for 14 days. Bulk specific gravity and bending strength tests were conducted on these wood wool boards. The results were as shown in Table 8.

【table】

Claims (1)

[Claims] 1. A mixture of coal ash (including fly ash and hearth bottom ash) generated from coal-fired power plants, etc. and an aqueous solution of phosphoric acid or its salt to 5 to 50 parts by weight of wood cutting material is P ₂ A method for producing a wood-based composite board, which comprises adding 95 to 50 parts by weight of an inorganic binder having a composition of 0.05 to 0.5 in terms of O ₅ /coal ash weight ratio, mixing and forming. 2. Claim 1, in which 1 to 20% by weight of the coal ash is replaced with at least one member selected from magnesium, calcium, aluminum, iron and silicon oxides or hydroxides, and asbestos. The method described in section. 3 Molding conditions are pressurized to 1-100Kg/ ^cm2 and/or
The method according to claim 1 or 2, wherein the method is heated to 20 to 200°C.